Project on Concrete Mix Design for various grades of Concrete
1A) AIM: To determine the Mix design for M35 grade concrete with fly ash.
INTRODUCTION: The common method of expressing the proportions of the materials in a concrete mix is in the form of parts of ratios of cement, sand, and coarse aggregates with cement being taken as unity.
The proportion should indicate whether it is indicated by volume or by mass. the water-cement ratio is generally expressed by mass. The amount of entrained air in concrete is generally expressed as a percentage of the volume of concrete. The amount of Admixtures is expressed with respect to the weight of the cement.
In this project, we are going to determine the mix design for M35 grade concrete whose compressive strength is 35 N/mm2.
PROCEDURE:
1) Determination of target mean strength:
f'ck=fck+k*s
f'ck=35+1.65*5.0
(As per IS 456-2000, K=1.65, and From Table-1 of IS:10262-2009,For M35 grade concrete standard deviation is taken as 5.0)
f'ck=43.25 N/mm2
2) Selection of water-cement ratio:
- From Table 5 of IS:456-2000, for severe exposure conditions, the Maximum free water-cement ratio is 0.45
- From compressive strength considerations adopt a water-cement ratio of 0.40
- Therefore w/c=0.40
3) Selection of water content:
- From above table, For slump range 25-50 mm, the maximum water content for 20 mm aggregate is 186 liters.
- For pumpable concrete, the Water content for 100 mm slump=186+6/100*186=197liters
- When superplasticizer is used as a water-reducing admixture, the water content can be reduced by 20%.
- Hence water content=197*0.80=158 liters
4) Calculation of cement content:
Water-cement raio=0.40
Cement content=158/0.40=395 kg/m3
From Table 5 of IS 456, the minimum cement content for severe exposure conditions=320 kg/m3
395 kg/m3>320 kg/m3.
Hence OK.
But here, we are replacing cement with 20% (Range = 10 to 35% ) fly ash i.e. 395 x 0.20 = 80kg
Therefore actual cement content = 315 kg/m3
5) Proportion of Volume of coarse aggregate and Fine aggregate content:
As per the reference table for a w/c=0.6, the proportion of sand is 35%
After adjustments, the sand percentage is reduced by 4%, i.e. 35-4=31%
- The volume of fresh concrete, V=Gross volume - Entrapped air=1-0.02 (i.e.2%)=0.98
- V=(W+C/SC+1/P*fa/Sfa)*1/1000
- Where W=Water Content
- C=Cement Content=395kg/m3
- Sc=Specific Gravity of cement=3.15
- P=Ratio of Fine aggregate percentage to Total aggregate percentage=31/100=0.31
- fa=Fine aggregate content
- Sfa=Specific gravity of fine aggregates=2.6
- V=(158+395/3.15+1/0.31*fa/2.6)*1/1000
- V=(158+125+3*fa/2.6)*1/1000
- Fine aggregate content, fa=561.46kg/m3
6) Coarse aggregate content: Ca=((1-P/P)*fa*(Sca/Sfa))
- Where Sca=Specific gravity of coarse aggregate
- Ca=((1-0.31/0.31) *561.46*(2.65/2.60))
- Coarse aggregate content, Ca=1273.73 kg/m3
7) Final mix proportions: (By Mass)
- Cement + Fly ash=395kg/m3
- Fine Aggregate=561kg/m3
- Coarse Aggregate=1274kg/m3
FINAL MIX PROPORTIONS=1: 1.42 : 3.22
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2A) Concrete mix design for M50 grade concrete without fly ash:
AIM: To determine the Mix design for M50 grade concrete without fly ash.
INTRODUCTION: The common method of expressing the proportions of the materials in a concrete mix is in the form of parts of ratios of cement, sand, and coarse aggregates with cement being taken as unity.
The proportion should indicate whether it is indicated by volume or by mass. the water-cement ratio is generally expressed by mass. The amount of entrained air in concrete is generally expressed as a percentage of the volume of concrete. The amount of Admixtures is expressed with respect to the weight of the cement.
In this project, we are going to determine the mix design for M50 grade concrete whose compressive strength is 50 N/mm2.
PROCEDURE:
1) Determination of target mean strength:
f'ck=fck+k*s
f'ck=50+1.65*5.0
(As per IS 456-2000, K=1.65, and From Table-1 of IS:10262-2009,For M50 grade concrete standard deviation is taken as 5.0)
f'ck=58.25 N/mm2
2) Selection of water-cement ratio:
- From Table 5 of IS:456-2000, for severe exposure conditions, the Maximum free water-cement ratio is 0.45
- From compressive strength considerations adopt a water-cement ratio of 0.38
- Therefore w/c=0.38
3) Selection of water content:
- From above table, For slump range 25-50 mm, the maximum water content for 20 mm aggregate is 180 liters.
- For pumpable concrete, the Water content for 100 mm slump=180+6/100*180=191liters
- When superplasticizer is used as a water-reducing admixture, the water content can be reduced by 20%.
- Hence water content=197*0.80=153 liters
4) Calculation of cement content:
Water-cement raio=0.38
Cement content=153/0.38=402 kg/m3
From Table 5 of IS 456, the minimum cement content for severe exposure conditions=320 kg/m3
402 kg/m3>320 kg/m3.
Hence OK.
5) Proportion of Volume of coarse aggregate and Fine aggregate content:
As per the reference table for a w/c=0.6, the proportion of sand is 35%
After adjustments, the sand percentage is reduced by 4.4%, i.e. 35-4.4=30.6%
- The volume of fresh concrete, V=Gross volume - Entrapped air=1-0.02 (i.e.2%)=0.98
- V=(W+C/SC+1/P*fa/Sfa)*1/1000
- Where W=Water Content
- C=Cement Content=402kg/m3
- Sc=Specific Gravity of cement=3.15
- P=Ratio of Fine aggregate percentage to Total aggregate percentage=31/100=0.31
- fa=Fine aggregate content
- Sfa=Specific gravity of fine aggregates=2.6
- V=(153+402/3.15+1/0.306*fa/2.6)*1/1000
- V=(153+128+3.26*fa/2.6)*1/1000
- Fine aggregate content, fa=556.42kg/m3
6) Coarse aggregate content: Ca=((1-P/P)*fa*(Sca/Sfa))
- Where Sca=Specific gravity of coarse aggregate
- Ca=((1-0.306/0.306) *556.42*(2.65/2.60))
- Coarse aggregate content, Ca=1286.21 kg/m3
7) Final mix proportions: (By Mass)
- Cement + Fly ash=402kg/m3
- Fine Aggregate=556kg/m3
- Coarse Aggregate=1286kg/m3
FINAL MIX PROPORTIONS=1: 1.38 : 3.19